1. Field of the Invention
The invention relates in general to a portable device and associated positioning method, and more particularly to a portable device that selectively uploads positioning information and associated positioning method.
2. Description of the Related Art
Many current portable devices, such as portable pads and mobile handsets, provide a positioning function through a Global Positioning System (hereinafter, GPS) carried therein.
In addition to providing positioning information to a user during normal operations of the user, a portable device equipped with the GPS positioning function is also capable of assisting the user in finding the portable device when the portable device is misplaced. Alternatively, when the portable device is utilized by a child, a parent or a teacher of the child may also learn the whereabouts of the child through the positioning function of the portable device.
FIG. 1 shows a schematic diagram of a user searching for a portable device via a tracking server.
With the prevalence of the Internet, a portable device 11 generally supports a function of a wireless communication network 13. For example, when the portable device 11 is a mobile handset, WiFi or Global System for Mobile Communications (hereinafter, GSM) may be utilized as the wireless communication network 13 for communicating with the external. When the portable device 11 is a portable tablet or a laptop computer, WiFi may be utilized as the wireless communication network 13.
When a user 16 needs to track a location of the portable device 11, based on a conventional approach, the location of the portable device 11 may be inquired through a tracking server 15 signally connected to the portable device 11.
The above conventional approach is described in detail below.
By utilizing a Short Message Service (SMS) or the Internet, a user sends a tracking instruction to the tracking server 15. The tracking server 15 then transmits the tracking instruction to the portable device 11 via the wireless communication network 13 (WiFi or GSM).
Upon receiving the notification from the tracking server 15, the portable device 11 first obtains positioning information through a positioning technology such as the GPS, and then returns the positioning information back to the tracking server 15 via the wireless communication network 13, for example.
However, such conventional technique for tracking the location of the portable device 11 is bound by certain restrictions.
First of all, the portable device 11 may not be situated in an environment having the wireless communication network 13. Or, the portable device 11 may be situated in an environment having a weak wireless communication network 13. As such, the tracking server 15 is hindered from establishing a connection with the portable device 11 via the wireless communication network 13.
Consequently, the portable device 11 does not have access to receiving the tracking instruction sent out by the tracking server 15. Further, the positioning information obtained by the portable device 11 cannot be transmitted to the tracking server 15 via the wireless communication network 13. In other words, the above tracking mechanism is largely affected by the communication status of the wireless communication network 13.
In a wireless communication network system, Media Access Control (hereinafter, MAC) addresses of all WiFi access points in the vicinity of the portable device are detected. After that, coordinates of the MAC addresses are fetched from a database and compared to obtain an actual location of the portable device.
Assuming that an obstruction is between the portable device 11 and the WiFi access points, and connection statuses between the portable device 11 and the WiFi access points are poor. In such case, positioning through WiFi is infeasible.
Secondly, the positioning function of the portable device 11 may also be restricted by the surrounding environment.
A basic principle of the GPS is that, signals are transmitted via several satellites revolving around the earth, and an actual location is calculated by cross-referencing paths of the signals. Yet, when a shelter obstructs signals coming from the sky, the GPS cannot successfully perform the positioning function.
However, a certain number of satellite signals are required for the portable device to cross-reference and cross-calculate its location. Hence, if insufficient number of the satellite signals are received, the actual location of the portable device 11 cannot be calculated.
Thus, once the GPS or the wireless network communication positioning system fails in providing the position information, the tracking mechanism of the portable device 11 also becomes invalid.
In other words, when employing the conventional approach for tracking the portable device 11, the portable device 11 can only be successfully tracked given that the portable device 11 is situated in a good network connection status with a serviceable positioning function. However, when either of the network connection status or the positioning function is unsatisfactory, the location of the portable device 11 may not be readily tracked and obtained by the above conventional approach.